One of the more common diagnostic tests a doctor may perform involves measuring the level of a chemical called creatinine in the urine or blood. The test is simple to perform and provides very useful information about how well your kidneys are performing at their task of waste management.
About Creatinine
Creatinine is a chemical produced primarily by your muscles during exertion and, to a smaller degree, as a byproduct of consuming meat. Creatinine has no practical purpose and is considered a waste product. If your kidneys are functioning properly, they filter creatinine out of the blood, and it is subsequently expelled from the body in the form of urine. If your kidneys are not performing to full potential, your serum and urine will show elevated levels of creatinine.
The Test
Your physician may want either a serum or urine analysis of your creatinine levels. In the case of a serum test, you may eat and drink normally before the test. A blood sample is drawn from a vessel in your arm and sent to the lab for analysis. For a urine creatinine clearance test, you will be asked to collect 24 hours' worth of urine samples in a sterile container. The urine is then sent to the lab for analysis. Both tests are used to assess kidney function.
Results
For adults, creatinine levels are generally between 0.5 and 1.5 milligrams per deciliter. However, factors like age, height and muscle mass can influence these values considerably without necessarily indicating kidney disease. Men normally exhibit a creatinine clearance rate of 97 to 137 milliliters per minute, while women have a creatinine clearance rate of between 88 and 128 milliliters per minute. Based on these guidelines, a serum creatinine of 0.71 is on the low end of the normal range.
Abnormal Results
High serum creatinine levels are typically caused by kidney damage but can also be the result of kidney stones, gout, heart disease, dehydration or muscular disease. Low serum creatinine levels can be caused by pregnancy, muscle degeneration, a low-protein diet or aging. High creatinine clearance levels may be caused by muscle injury, excessive exercise, burns, pregnancy or carbon monoxide poisoning. Low clearance levels may be the result of kidney or liver damage, heart failure or dehydration.
